Linux DPT Hardware RAID HOWTO

Linux DPT Hardware RAID HOWTO
Ram Samudrala ([email protected])
v1.4, 9 April 1999

How to set up hardware RAID under Linux.
______________________________________________________________________

Table of Contents

1. Introduction

2. Supported controllers

2.1 DPT controllers
2.2 ICP vortex controllers

3. What hardware should be used?

3.1 Controller type
3.2 Enclosure type

4. Installation

4.1 Installing and configuring the hardware
4.2 Configuring the kernel
4.3 Bootup messages

5. Usage

5.1 fdisk, mke2fs, mount, etc.
5.2 Hotswapping
5.3 Performance

6. Features in the EATA DMA driver

7. Troubleshooting

7.1 Upon bootup, no SCSI hosts are detected
7.2 RAID configuration shows up as N different disks
7.3 Machine/controller is shut down in the middle of a format
7.4 If all fails...

8. References

9. Acknowledgements

______________________________________________________________________

1. Introduction

This document describes how to set up SCSI hardware RAID, focusing
mainly on host-based adapters from DPT, though the principles applied
here are fairly general.

Use the information below at your own risk. I disclaim all
responsibility for anything you may do after reading this HOWTO. The
latest version of this HOWTO will always be available at
http://www.ram.org/computing/linux/dpt_raid.html.

For the purposes of this HOWTO, I am assuming you have only a Linux
system running. Also, note that I've only tried this out with the DPT
Smartcache IV PM2144UW and PM3334UW controllers, with DPT (SmartRAID
tower) and Wetex enclosures, and I have no experience with other
setups. So things may be different for your setup.

2. Supported controllers

Currently the only well-supported host-based hardware RAID controller
(i.e, a controller for which there exists a driver under Linux) is one
that is made by DPT <http://www.dpt.com>. However, there exist other
host-based and scsi-to-scsi controllers which may work under Linux.
These include the ones made by Syred <http://www.syred.com>, ICP-
Vortex <http://www.icp-vortex.com>, and BusLogic
<http://www.mylex.com>. In addition, there exist plenty of SCSI-to-
SCSI controllers. See the RAID solutions for Linux page
<http://linas.org/linux/raid.html> for more info.

If, in the future, there is support for other controllers, I will do
my best to incorporate that information into this HOWTO. Please send
me any such information you think is appropriate for this HOWTO.

2.1. DPT controllers

This document is currently DPT-oriented. Essentially all the
SmartRAID IV controllers are supported.

2.2. ICP vortex controllers

ICP vortex has a complete line of disk array controllers which support
Linux. The ICP driver is in the Linux kernel since version 2.0.31 All
major Linux Distributors S.u.S.e., LST Power Linux, Caldera and Red
Hat support the ICP controllers as boot/installation controllers. The
RAID system can easily be configured with our ROMSETUP (you do not
have to boot MS-DOS for configuration!).

With the monitoring utility GDTMON it is possible to manage the
complete ICP RAID system during operation (check transferrates, set
parameters for the controller and hard disks, exchange defective hard
disks, etc.). Currently available are: 1 and 2 channel wide and ultra
SCSI controller for RAID 0 and RAID 1 1, 2, 3 and 5 chn. wide and
ultra SCSI controller for RAID 0, 1, 4, 5 and 10 1 and 2 channel wide
and ultra2 LVDS SCSI controller for RAID 0 and RAID 1 1, 2, 3 and 5
chn. wide and ultra2 LVDS SCSI controller for RAID 0, 1, 4, 5 and 10 1
and 2 port Fibre Channel contollers for RAID 0, 1, 4, 5 and 10 Pretty
soon there will be also 64-bit controllers available.

3. What hardware should be used?

3.1. Controller type

Given all these options, if you're looking for a RAID solution, you
need to think carefully about what you want. Depending on what you
want to do, and which RAID level you wish to use, some cards may be
better than others. SCSI-to-SCSI adapters may not be as good as host-
based adapters, for example (see the DPT comparison between host-based
and SCSI-to-SCSI adapters <http://www.dpt.com/hstvscsi.htm> for why
this is the case). Michael Neuffer ([email protected]),
the author of the EATA-DMA driver, has a nice discussion about this on
his Linux High Performance SCSI and RAID page <http://www.uni-
mainz.de/~neuffer/scsi/>.

3.2. Enclosure type

The enclosure type affects the hot swapability of the drive, the
warning systems (i.e., whether there will be indication of failure,
and whether you will know which drive has failed), and what kind of
treatment your drive receives (for example, redundant cooling and
power supplies). We used the DPT supplied enclosures for an initial
RAID-5 system of 18 GB, but they are expensive. We are now using a
Wetex enclosure (http://www.wetex.com/), which have the same features
as the DPT ones, but are about 1/4 of the cost. The Wetex enclosure
system (14 bays) we use is composed of two RAID-5 arrays, with sizes
of 45 GB and 63 GB.

4. Installation

4.1. Installing and configuring the hardware

Refer to the instruction manual to install the card and the drives.
For DPT, since a storage manager for Linux doesn't exist yet, you need
to create a MS-DOS-formatted disk with the system on it (usually
created using the command "format /s" at the MS-DOS prompt). You will
also be using the DPT storage manager for MS-DOS, which you should
probably make a copy of for safety.

Once the hardware is in place, boot using the DOS system disk. Replace
the DOS disk with the storage manager. And invoke the storage manager
using the command:

a:\ dptmgr

Wait a minute or so, and you'll get a nice menu of options. Configure
the set of disks as a hardware RAID (single logical array). Choose
"other" as the operating system.

The MS-DOS storage manager is a lot easier to use with a mouse, and so
you might want to have a mouse driver on the initial system disk you
create.

Technically, it should be possible to run the SCO storage manager
under Linux, but it may be more trouble than its worth. It's probably
more easier to run the MS-DOS storage manager under Linux.

4.2. Configuring the kernel

You will need to configure the kernel with SCSI support and the
appropriate low level driver. See the Kernel HOWTO
<http://sunsite.unc.edu/mdw/HOWTO/Kernel-HOWTO.html> for information
on how to compile the kernel. Once you choose "yes" for SCSI support,
in the low level drivers section, select the driver of your choice
(EATA DMA or EATA ISA/EISA/PCI for most EATA DMA compliant (DPT)
cards, EATA PIO for the very old PM2001 and PM2012A from DPT). Most
drivers, including the EATA DMA and EATA ISA/EISA/PCI drivers, should
be available in recent kernel versions.

Once you have the kernel compiled, reboot, and if you've set up
everything correctly, you should see the driver recognising the RAID
as a single SCSI disk. If you use RAID-5, you will see the size of
this disk to be 2/3 of the actual disk space available.

4.3. Bootup messages

The messages you see upon bootup if you're using the EATA DMA driver
should look something like this:

EATA (Extended Attachment) driver version: 2.59b
developed in co-operation with DPT
(c) 1993-96 Michael Neuffer, [email protected]
Registered HBAs:
HBA no. Boardtype Revis EATA Bus BaseIO IRQ DMA Ch ID Pr QS S/G IS
scsi0 : PM2144UW v07L.Y 2.0c PCI 0xef90 11 BMST 1 7 N 64 252 Y
scsi0 : EATA (Extended Attachment) HBA driver
scsi : 1 host.
Vendor: DPT Model: RAID-5 Rev: 07LY
Type: Direct-Access ANSI SCSI revision: 02
Detected scsi disk sda at scsi0, channel 0, id 8, lun 0
scsi0: queue depth for target 8 on channel 0 set to 64
scsi : detected 1 SCSI disk total.
SCSI device sda: hdwr sector= 512 bytes. Sectors= 35591040 [17378 MB] [17.4 GB]

(The above display is for a setup with a single DPT SCSI controller,
configured as RAID-5, with three disks of 9 GB each.)

The messages you see upon bootup if you're using the EATA ISA/EISA/PCI
driver should look something like this:

aic7xxx: <Adaptec AHA-294X SCSI host adapter> at PCI 15
aic7xxx: BIOS enabled, IO Port 0x7000, IO Mem 0x3100000, IRQ 15, Revision B
aic7xxx: Single Channel, SCSI ID 7, 16/16 SCBs, QFull 16, QMask 0x1f
EATA0: address 0x7010 in use, skipping probe.
EATA0: 2.0C, PCI 0x7410, IRQ 11, BMST, SG 252, MB 64, tc:y, lc:y, mq:62.
EATA0: wide SCSI support enabled, max_id 16, max_lun 8.
EATA0: SCSI channel 0 enabled, host target ID 6.
EATA/DMA 2.0x: Copyright (C) 1994-1997 Dario Ballabio.
scsi0 : Adaptec AHA274x/284x/294x (EISA/VLB/PCI-Fast SCSI) 4.1.1/3.2.1
scsi1 : EATA/DMA 2.0x rev. 3.11.00
scsi : 2 hosts.
scsi0: Scanning channel A for devices.
Vendor: IBM OEM Model: DFHSS2F Rev: 1818
Type: Direct-Access ANSI SCSI revision: 02
Detected scsi disk sda at scsi0, channel 0, id 0, lun 0
Vendor: SEAGATE Model: ST41650 TX Rev: DG01
Type: Direct-Access ANSI SCSI revision: 02
Detected scsi disk sdb at scsi1, channel 0, id 0, lun 0
Vendor: TEAC Model: FC-1 GF 00 Rev: RV L
Type: Direct-Access ANSI SCSI revision: 01 CCS
Detected scsi removable disk sdc at scsi1, channel 0, id 3, lun 0
Vendor: SONY Model: CD-ROM CDU-541 Rev: 2.6a
Type: CD-ROM ANSI SCSI revision: 02
Detected scsi CD-ROM sr0 at scsi1, channel 0, id 5, lun 0
EATA0: scsi1, channel 0, id 0, lun 0, cmds/lun 21, sorted, tagged.
EATA0: scsi1, channel 0, id 3, lun 0, cmds/lun 21, sorted.
EATA0: scsi1, channel 0, id 5, lun 0, cmds/lun 21, sorted.
scsi : detected 1 SCSI cdrom 3 SCSI disks total.
SCSI device sda: hdwr sector= 512 bytes. Sectors= 4404489 [2150 MB] [2.2 GB]
SCSI device sdb: hdwr sector= 512 bytes. Sectors= 2779518 [1357 MB] [1.4 GB]
SCSI device sdc: hdwr sector= 256 bytes. Sectors= 4160 [1 MB] [0.0 GB]

(The above display is for a setup wih two SCSI controllers, DPT
PM3224W and and Adaptec AHA2940.)

5. Usage

5.1. fdisk, mke2fs, mount, etc.

You can now start treating the RAID as a regular disk. The first thing
you'll need to do is partition the disk (using fdisk). You'll then
need to set up an ext2 filesystem. This can be done by running the
command:

% mkfs -t ext2 /dev/sdxN

where /dev/sdxN is the name of the SCSI partition. Once you do this,
you'll be able to mount the partitions and use them as you would any
other disk (including adding entries in /etc/fstab).

5.2. Hotswapping

We first tried to test hotswapping by removing a drive and putting it
back in the DPT-supplied enclosure/tower (which you buy for an
additional cost). Before we could carry this out to completion, one
of the disks failed (as I write this, the beeping is driving me
crazy). Even though one of the disks failed, all the data on the RAID
drive is accessible.

Instead of replacing the drive, we just went through the motions and
put the same drive back in. The drive rebuilt itself and everything
seems to be okay. During the time the disk had filed, and during the
rebuilding process, all the data was accessible. Though it should be
noted that if another disk had failed, we'd have been in serious
trouble.

5.3. Performance

Here's the output of the Bonnie program, on a 2144 UW with 9x3=17 GB
RAID 5 setup, using the EATA DMA driver. The RAID is on a dual
processor Pentium Pro machine running Linux 2.0.33. For comparison,
the Bonnie results for the IDE drive on that machine are also given.

-------Sequential Output-------- ---Sequential Input-- --Random--
-Per Char- --Block--- -Rewrite-- -Per Char- --Block--- --Seeks---
MB K/sec %CPU K/sec %CPU K/sec %CPU K/sec %CPU K/sec %CPU /sec %CPU
RAID 100 9210 96.8 1613 5.9 717 5.8 3797 36.1 90931 96.8 4648.2 159.2
IDE 100 3277 32.0 6325 23.5 2627 18.3 4818 44.8 59697 88.0 575.9 16.3

Some people have disputed the above timings (and rightly so---I've
been unable to try it out on our machines since they're completely
loaded) because the size of the file used may have led to it being
cached (resulting in an unusually good performance report). Here are
some timings with a 3344 UW controller:

-------Sequential Output-------- ---Sequential Input-- --Random--
-Per Char- --Block--- -Rewrite-- -Per Char- --Block--- --Seeks---
MB K/sec %CPU K/sec %CPU K/sec %CPU K/sec %CPU K/sec %CPU /sec %CPU
1000 1714 17.2 1689 6.0 1200 5.7 5263 40.2 7023 12.1 51.3 2.2

And here are some timings on a host-based RAID system:

-------Sequential Output-------- ---Sequential Input-- --Random--
-Per Char- --Block--- -Rewrite-- -Per Char- --Block--- --Seeks---
MB K/sec %CPU K/sec %CPU K/sec %CPU K/sec %CPU K/sec %CPU /sec %CPU
64 7465 100.0 70287 98.7 37012 97.7 8074 99.2 *****100.3 ***** 196.6
128 7289 99.3 67595 98.5 35294 98.6 7792 97.6 *****100.3 ***** 195.8
256 7222 98.8 44844 69.6 16096 51.8 5787 72.7 ***** 99.8 ***** 85.2
512 7138 98.4 13871 23.2 7888 29.3 7183 89.3 16488 27.2 1585. 11.5
1024 6908 95.8 12270 21.5 7161 25.4 7373 90.4 16527 28.2 123.8 1.8
2047 6081 84.1 12664 22.6 7191 25.6 7289 89.5 16573 28.5 75.0 1.2

***** results exceed column width (> 100 MB/sec, > 10000 seeks/sec)

host: Dual PII 400 MHz, 2 x U2W, 512 MB RAM, no internal disks
RAID: IFT 3102 UA 128 MB Cache, RAID-5, 6 x 9 GB
OS: SuSE Linux 6.0 with Kernel 2.2.3

6. Features in the EATA DMA driver

This section describes some of the commands available under Linux to
check on the RAID configuration. Again, while references to the
eata_dma driver is made, this can be used to check up on any driver.

To see the configuration for your driver, type:

% cat /proc/scsi/eata_dma/N

where N is the host id for the controller. You should see something
like this:

EATA (Extended Attachment) driver version: 2.59b
queued commands: 353969
processed interrupts: 353969

scsi0 : HBA PM2144UW
Firmware revision: v07L.Y
Hardware Configuration:
IRQ: 11, level triggered
DMA: BUSMASTER
CPU: MC68020 20MHz
Base IO : 0xef90
Host Bus: PCI
SCSI Bus: WIDE Speed: 10MB/sec.
SCSI channel expansion Module: not present
SmartRAID hardware: present.
Type: integrated
Max array groups: 7
Max drives per RAID 0 array: 7
Max drives per RAID 3/5 array: 7
Cache Module: present.

Type: 0
Bank0: 16MB without ECC
Bank1: 0MB without ECC
Bank2: 0MB without ECC
Bank3: 0MB without ECC
Timer Mod.: present
NVRAM : present
SmartROM : enabled
Alarm : on
Host<->Disk command statistics:
Reads: Writes:
1k: 0 0
2k: 0 0
4k: 0 0
8k: 0 0
16k: 0 0
32k: 0 0
64k: 0 0
128k: 0 0
256k: 0 0
512k: 0 0
1024k: 0 0
>1024k: 0 0
Sum : 0 0

To get advanced command statistics, type:

% echo "eata_dma latency" > /proc/scsi/eata_dma/N

Then you can do a:

% cat /proc/scsi/eata_dma/N

to get more detailed statistics.

To turn off advanced command statistics, type:

% echo "eata_dma nolatency" > /proc/scsi/eata_dma/N

7. Troubleshooting

7.1. Upon bootup, no SCSI hosts are detected

This could be due to several reasons, but it's probably because the
appropriate driver is not configured in the kernel. Check and make
sure the appropriate driver (EATA-DMA or EATA ISA/EISA/PCI for most
DPT cards) is configured.

7.2. RAID configuration shows up as N different disks

The RAID has not been configured properly. If you're using a DPT
storage manager, you need to configure the RAID disks as a single
logical array. Michael Neuffer ([email protected])
writes: "When you configure the controller with the SM start it with
the parameter /FW0 and/or select Solaris as OS. This will cause the
array to be setup to be managed internally by the controller."

7.3. Machine/controller is shut down in the middle of a format

As stated in the DPT manual, this is clearly a no-no and might require
the disks to be returned to the manufactured, since the DPT Storage
Manager might not be able format it. However, you might be able to
perform a low level format on it, using a program supplied by DPT,
called clfmt in their utilities page
(http://www.dpt.com/techsup/sr4utils.htm). Read the instructions after
unzipping the clfmt.zip file on how to use it (and use it wisely).
Once you do the low level format, you might be able to treat the disks
like new. Use this program carefully!

7.4. If all fails...

Read the SCSI-HOWTO again. Check the cabling and the termination.
Try a different machine if you have access to one. The most common
cause of problems with SCSI devices and drivers is because of faulty
or misconfigured hardware. Finally, you can post to the various
newsgroups or e-mail me, and I'll do my best to get back to you.

8. References

The following documents may prove useful to you as you set up RAID:

DPT Technology Library <http://www.dpt.com/library.htm>

EATA-DMA homepage <http://www.uni-
mainz.de/~neuffer/scsi/dpt/index.html>

Linux Disk HOWTO <http://sunsite.unc.edu/mdw/HOWTO/Disk-HOWTO.html>

Linux Kernel HOWTO <http://sunsite.unc.edu/mdw/HOWTO/Kernel-
HOWTO.html>

Linux SCSI HOWTO <http://sunsite.unc.edu/mdw/HOWTO/SCSI-HOWTO.html>

Multi Disk System Tuning HOWTO
<http://www.nyx.net/~sgjoen/disk.html>

RAID Solutions for Linux <http://linas.org/linux/raid.html>

9. Acknowledgements

The following people have been helpful in getting this HOWTO done:

Andreas Koepf ([email protected])

Boris Fain ([email protected])

Dario Ballabio ([email protected])

Heiko Rommel ([email protected])

Jos Vos ([email protected])

Michael Neuffer ([email protected])

Ralph Wallace ([email protected])

Russell Brown ([email protected])

Syunsuke Ogata ([email protected])

Tom Brown ([email protected])